Fig. 6

PCA analysis of mandible shape between M. m. helgolandicus and reference populations. a General comparison with multiple populations. The first two axes of a PCA scatter plot are shown. b Comparison of each time sample from Heligoland with the reference population from Germany. The first two axes of a PCA scatter plot are shown on top; the shape changes along the first two PCs between M. m. helgolandicus and M. m. domesticus populations are depicted as wire-frame graphs at the bottom. Shape changes are from grey (M. m. domesticus) to red (M. m. helgolandicus). The red arrow points to the individual that represents a recent immigrant (see text)